Polymeric additives are used in automatic machine dishwashing detergent formulations as phosphate substitutes, builders, thickeners, processing aids, film-control agents and spot-control agents. Unlike many other detergent formulations, it is critical that automatic machine dishwashing detergents are low foaming systems. Foam interferes with the mechanical washing action of the water which is sprayed in the machine. This requirement limits the types of polymeric additives and surfactants which can be used in an automatic machine dishwashing detergent formulation.
United Kingdom Patent No. 2,104,091 to Takashi et al. discloses amphoteric copolymers containing as polymerized units cationic vinyl monomers and anionic vinyl monomers for use in detergent compositions. The mole ratio of cationic vinyl monomer to anionic vinyl monomer is from 1:99 to 99:1 and is preferably 20:80 to 80:20. The molecular weight of the polymers is from 1,000 to 3,000,000. All of the examples employ copolymers having a 1:1 molar ratio of cationic vinyl monomer to anionic vinyl monomer. The polymers are disclosed to be useful for enhancing the foaming power of surfactant-based liquid detergent compositions.
U.S. Pat. No. 4,784,789 to Jeschke et al. discloses the use of certain copolymers for use in liquid hard-surface cleaner formulations to provide an anti-static finish on the surfaces. The polymers described therein are those taught by U.K. Patent No. 2,104,091, discussed above, which contain at least one mole of nitrogen-containing acrylic acid derivative per mole of acrylic acid.
U.S. Pat. No. 4,075,131 to Sterling discloses the use of zwitterionic copolymers for use in shampoos. The copolymers disclosed therein have a molar ratio of basic monomer to acidic monomer in the range of from 0.6:1 to 1.5:1.
U.S. Pat. No. 4,534,892 to Suzuki et. al discloses the use of crosslinked copolymers of acidic and basic monomers as dispersants for water-insoluble fine powders in liquid detergents. It further discloses that the copolymers effectively disperse the solids without interfering with the foaming properties of the detergent compositions.
Japanese Patent Application 59-135293A discloses terpolymers comprising at least 10 mole percent of each of (1) an anionic vinyl monomer, (b) a cationic vinyl monomer, and (c) a nonionic vinyl monomer, wherein the molar ratio of anionic vinyl monomer to cationic vinyl monomer is from 1:2 to 2:1. It further discloses that the polymers increase the detergency of detergent compositions, especially when used with surfactants.
Development of machine dishwashing detergents using substitutes for phosphate containing compounds has been addressed in the patent literature. U.S. Pat. No. 4,203,858 teaches using a low molecular weight polyacrylic acid in a phosphate free machine dishwashing composition. U.S. Pat. No. 4,608,188 teaches the use of a maleic acid/acrylic acid copolymer.
Other patents which include polymeric materials in dishwashing detergents are European Patent 132,792, German Patent DE 3627773-A, and UK Patent Application GB 2,203,163-A. EP 132,792 teaches certain cleaning compositions for washing dishes in automatic dishwashers. The compositions contain from 1 to 8 weight percent of a polycarboxylic acid having molecular weight of 12,000 to 40,000. In addition, the detergent contains surfactants and standard additives such as bleaching agents, biocides, perfumes, foaming-inhibitors, and/or solubilizers. The polymer can be poly(acrylic acid), poly(methacrylic acid), or polymers of maleic acid or fumaric acid and ethylene or propylene.
The object of the present invention is to provide novel water-soluble terpolymers and a method for their preparation. Another object of the present invention is to provide methods of enhancing the spotting and filming control of automatic machine dishwashing detergent formulations.